KR100383307B1 - Arrays of impingement jets with inserted effusion holes - Google Patents

Abstract

The present invention relates to an array collision jet cooling technology of the insertion outlet hole installation method to change the discharge method of the array collision jet to improve the cooling efficiency.

The array colliding jet of the present invention is an angle arranged on the jet jet plate 1 so that the fluid after cooling the collision surface 3 escapes transversely and exits vertically without affecting other jetting jets. It is made by installing a separate outflow hole 5 between the injection jet holes (2), characterized in that it comprises a projection (7) to extend the inlet side of the outflow hole closer to the impact surface to make an insertion type outflow hole. As a result, an increase in the discharge flow in the vicinity of the outlet hole is suppressed, the thickness of the boundary layer is reduced, and in particular, the re-suction flow is reduced, thereby increasing the overall average heat / material transfer coefficient.

Description

Arrays of impingement jets with inserted effusion holes

The present invention relates to an array collision jet cooling technology of the insertion outlet hole installation method to change the discharge method of the array collision jet to improve the cooling efficiency.

In practical applications of cooling technology, several collision jets are used together in a large area, which is called arrays of impingement jets. The collision jet has a high heat transfer and mass transfer effect locally. Because of these advantages, it is widely used in various fields. For example, in order to increase the efficiency of gas turbine engines, it is essential to increase the turbine inlet temperature, which is limited by the material, which leads to the need for an effective cooling method. In the steel industry, even in the processes of steel making, steelmaking, continuous casting, rolling, etc., high temperature waste or ingots are required, and thus effective cooling is required for extending the life of contact elements and reducing the use of cooling water.

However, improper cooling may cause residual heat stress in the rolled steel sheet, which may cause deformation later. Therefore, it is essential to develop an effective collision jet cooling technique to improve product quality. In addition, as the heat generation per unit volume rapidly increases with the integration and miniaturization of computers in recent years, local cooling has become important, leading to the application of impact jets to the cooling of computer chips. It should be chosen to satisfy two conditions well: high heat / mass transfer coefficient and uniformity of surface temperature distribution.

According to these conditions, the study on the array collision jet has been conducted until now, as shown in FIG. 1, the spacing S between the jet hole 2 formed in the jet jet plate 1 and another jet hole 2a adjacent to each other. The method and the gap between the jet nozzle and the impact surface 3 have been carried out. However, as shown in FIG. 1, the fluids discharged to the outside after hitting the collision surface 3 adversely affect other adjacent jets. Not only does it cause an overall non-uniform cooling effect, but also shows a low heat transfer effect on average. This effect is very large when the spacing H between the jet jet plate 1 and the collision surface 3 is small.

Existing cooling technology using array collision jet has only been applied to the basic application of simply injecting fluid through multiple injection devices. Therefore, the amount of cooling fluid used is relatively high and the power for supplying the cooling fluid is increased due to relatively low cooling performance. In particular, the outlet is usually located next to it, so the occurrence of yellow flow is inevitable. And this lateral flow generates thermal stress due to the reduction and nonuniformity of the overall heat / mass transfer effect.

This can be seen through many dimensionless numbers such as non-dimensionalized number, Reynolds number, Prandtl number, Nusselt number, etc., which exhibit certain characteristics in flow or heat transfer.

Heat transfer coefficient can be obtained through Nusselt number = Nu, a dimensionless number representing heat transfer. (Larger value indicates higher cooling effect).

Where h is the convective heat transfer coefficient

d: jet diameter

k: thermal conductivity,

The mass transfer coefficient can be obtained from the Sherwood number = Sh, a dimensionless number representing the mass transfer. Appears.

Where hm is the convective-dimensionalized number

d: jet jet diameter

Dnaph: Naphthalene vapo diffusivity in air.

The similarity relationship between heat transfer and mass transfer is

Is,

Where Pr is the number of plants,

Sc is a schmidt number,

n is an index determined by experiment.

Based on the above relations, the results of material transfer experiments can be converted to heat transfer and analyzed.

In the conventional method of discharging the colliding jet, which is related to the heat / mass transfer effect and uniformity, transverse flow is inevitable.

As mentioned above, what is important in the array collision jet is how uniformly it can have a high heat transfer effect. The array collision jet technology currently applied has various unfavorable results due to lateral flow. Figure 2 shows the heat / mass transfer characteristics of the general configuration colliding jet with a lateral flow, since the configuration of the colliding colliding jet symmetry, when the working fluid is discharged to the right with the center of the center jet x / d = 0.0 Shows local heat / mass transfer properties. As shown in FIG. 2A, when the jetting jet exit and the collision surface have a large distance (H / d = 10), the influence of the transverse flow does not appear so large. However, in the case of the interval (H / d = 4) of FIG. 2 (b) and H / d = 2 of FIG. 2 (c), it is found that the distribution of the dimensionless heat / mass transfer coefficient is gradually changed in the array collision jet. When the distance H / d = 0.5 becomes very small as shown in Fig. 2 (d), a very large change occurs downstream.

At y / d = 0, x / d = 0, 6, 12, 18, and 24 where the local value passes through the center of the jet, the value increases as it goes downstream. The values of y / d = 3 appear very small downstream. Therefore, when the gap is small, the overall heat / mass transfer effect becomes more uneven due to the effect of transverse flow.

Figure 3 shows the overall average heat / mass transfer coefficient according to H / d. It has the maximum mean value in H / d. The reason why H / d increases and decreases is mainly due to the reduction in the momentum of the jet hitting the collision surface. However, if H / d is less than 2, the average value is due to the transverse flow inevitably shown by the discharge outlet shape. In summary, the transverse flow results in low heat / mass transfer effects and severe heat / mass transfer nonuniformities at narrow intervals.

Therefore, an object of the present invention is to improve the cooling performance of the array collision jet through the change of a simple discharge method consisting of the fluid discharge method using the insertion outlet hole in order to minimize the influence of the transverse flow.

A feature of the present invention for achieving this object is an arrangement consisting of a jet injection plate having a collision surface to be cooled and having a plurality of jet holes which are spaced at arbitrary intervals with respect to the collision surface to cause the cooling fluid to strike the collision surface. In the impingement jet, the colliding jet of jets, each jet jet arranged in the jet jet plate so that the fluid after cooling the collision surface exits in the vertical direction without affecting the other jet jet while passing in the transverse direction It is made by inserting a separate outlet hole pipe between the holes, the outlet hole pipe is to close the inlet side of the outlet hole pipe to the collision surface to reduce the re-suction flow from the impact surface to the outlet hole of the outlet hole pipe. It is characterized in that it is provided with an extended protrusion. Thus the outflow hole pipe is inserted into the jet jet plate Create and insert-type outflow hole for positioning close to the inlet to the impact surface, it is possible to suppress the decrease and increase the flow of the boundary layer thickness in the wall jet region, the better heat / mass transfer effects.

1 is a schematic view of a general arrangement collision jet and its flow flow

2A to 2D are charts showing the dimensionless heat / mass transfer coefficient distribution in the array collision jet of FIG.

Figure 3 is a transverse flow diagram according to the overall average dimensionless heat / mass transfer coefficient distribution according to the change of the gap between the impact surface and the jet jet plate in a general arrangement collision jet

Figure 4 shows an array collision jet according to the invention (a) is a plan view (b) is a cross-sectional view

Figure 5 shows an example of the shape deformation of the jet hole and the outlet hole according to the present invention (a) is an example of the shape change of the outlet side of the injection jet hole, (b) shows an example of the shape condition change of the inlet hole exit drawing

Figure 6 is a graph of the overall average heat / mass transfer coefficient of the outflow hole transverse flow in accordance with the present invention

Figure 7 is a numerical analysis of the speed characteristics of the discharge method according to the installation conditions of the outlet hole and the insertion outlet hole (a) the outlet hole (b) is the insertion outlet hole

Figure 8 is a table of speed comparison according to the numerical analysis of the collision surface under the conditions (a) the outflow hole (b) the insertion outflow hole

9 and 10 are diagrams for comparing isothermal / mass transfer coefficients in the collision surface, respectively (a) is a general arrangement collision jet discharge method, (b) is a comparison diagram comparing the discharge method of the installation outlet hole insertion

FIG. 11 shows the dimensionless heat / mass transfer coefficient of the colliding jet, (a) is a straight line passing through the center of the jet hole with respect to H / d = 1.5 in the collision plane, and (b) is a straight line passing through the center of the outlet hole to be. This is a comparison chart showing the difference according to the application method of insertion outlet hole (change of Hm / d).

12 is a chart showing the overall average heat / mass transfer coefficient according to the change of the insertion exit hole inlet height at various collision surface-outlet hole inlet heights.

* Description of the symbols for the main parts of the drawings *

1: Jet injection plate 2: Jet hole

3: Collision side 4: Jet jet exit

5: (insertion) outlet hole 6: protrusion

7: protrusion 8: gradient back

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 4 to 12.

The present invention is to obtain a good heat / mass transfer effect and uniformity in the collision surface (3) by changing the discharge method of the array collision jet as shown in FIG. Until now, the use of the colliding jet has inevitably caused the lateral flow. However, in order to reduce the lateral flow, the present invention inserts the outflow hole pipe 5 on the same surface as the jet ejection outlet 4 of the jet jet plate 1. Was installed. The installation of the outflow hole pipe 5 is, for example, by first making a hole therebetween in consideration of the position and spacing of the jet injection hole formed in the jetting plate and inserting and fixing the outflow hole pipe 5 therein, and simply Outlet holes may be formed in the jetting plate. The number of injection jet holes 2 may vary according to the area of the cooling collision surface 3.

The shape condition of the array collision jet according to the installation of the insertion outlet hole pipe 5 is that when the diameter of the injection jet hole 2 is d,

The spacing S / d between the jet jet hole 2 and the jet jet hole 2 is 3 to 10,

The distance H / d between the jet injection outlet 4 and the collision surface 3 is 0.5 to 10,

Outflow hole diameter size (de / d) of the outflow hole pipe 5 is 1 to 3 (where de means the diameter size of the outflow hole),

The distance (Hm / d) between the insertion outlet hole pipes 5 at the collision surface 3 is 0.5 to 9,

The injection jet hole 2 arrangement method selectively applies an in-line or staggered method.

In addition, in order to change the turbulence intensity and momentum of the flow in the collision surface (3), the shape and length of the outlet (4) of the injection jet hole (2) as shown in Fig. 5 (a) extends to the protrusion (6) You can change it. In addition, in order to reduce the re-intake of the working fluid into the injection jet hole (2), as shown in Fig. 5 (b) to form the inlet side of the outflow hole pipe 5 as an extended protrusion (7) or this protrusion (7) It can be changed by treating it with a gradient surface 8 which expands the space of.

When explaining the characteristics of the jet jet of the present invention having the insertion outlet hole pipe 5 compared to the conventional colliding jet jet flow and the effect on the colliding jet jet through this as follows.

What is important in an array collision jet is how uniformly it can have a high heat transfer effect. The array collision jet technology currently applied has various unfavorable results due to lateral flow. This can be seen through FIGS. 2 and 3, where the overall heat / mass transfer effect is more non-uniform due to the effect of transverse flow when the gap is small. In summary, lateral flow results in low heat / mass transfer effects and severe heat / mass transfer nonuniformities at narrow intervals.

On the other hand, when the outflow hole pipe 5 is installed, as shown in FIG. 6, since the transverse flow can be reduced at a particularly low interval (H / d = 0.5 to 1.5), a good heat / mass transfer effect can be obtained. 6 is a graph comparing the average heat / mass transfer coefficients of the outlet hole installation and the transverse flow.

According to the present invention, as an outgoing colliding jet which controls the discharge of flow after the collision jet is injected into the collision surface 3 through the jet hole 2, the low average heat / mass transfer coefficient and imbalance represented by the transverse flow Many of the shortcomings, such as the distribution of heat / mass transfer coefficients, could be overcome, and this effect was especially large when the spacing between the jet jet plate 1 and the impingement surface 3 was small. However, the presence of the outflow hole 5 formed on the same surface as the jet injector 1 due to the geometrical factors causes a re-entrainment phenomenon of the discharge fluid into the injection jet hole 2. In addition, when the flow is discharged, inevitably upstream flow in the wall jet region develops a boundary layer. These factors contribute to the reduction of heat / mass transfer. Inserted outlet hole pipe (5) is designed to overcome the disadvantages of the above-described outflow colliding jet. As shown in FIG. 5 (a) and (b), the inlet of the insertion outlet hole pipe 5 is closer to the collision surface 3 than the injection jet hole 2 due to the protrusion 7, thereby reducing the resorption effect. Good heat / mass transfer effects can be expected by reducing upflow and inhibiting boundary layer development. Similarly, the protrusion 7 may be formed as a gradient surface 8 to accelerate the flow of the flow to further reduce the resorption phenomenon, and also the exit shape and length of the jet hole 2 may be defined by the protrusion 6. It is also possible to extend through it to change the turbulence intensity and momentum of the flow occurring in the collision surface 3.

7 is a result of numerical calculation of the velocity distribution in the vicinity of y / d = 3.0, where (a) is for installing an outlet hole and (b) is for installing an insertion type outlet hole (Hm / d = 1.0). (Insert outflow hole is limited to the inlet side closer to the collision surface (3) through an extension, such as a projection (7)). In the case of the array colliding jet with the insertion type outlet hole pipe 5, the tip of the outlet hole does not coincide with the height of the jet jet plate 1 under the same conditions as the existing apparatus for colliding colliding colliding jet. To be close. After exiting the jet, the upward velocity component of the discharge flow must be present to exit the upper jet hole in the wall jet region. In the case of the inlet outlet pipe 5, the discharge flow is increased near the center of the outlet hole, and the boundary layer thickness is thinner.

(A) and (b) of FIG. 8 compare the speeds at the collision surface of the outflow hole and the insertion outflow hole (Hm / d = 1.0), respectively, under the numerical analysis and z / d = 0.1, where z / d = 0.1 In other words, it shows the velocity distribution at a height of 1 mm away from the collision surface. In the figure, the brighter part represents the higher speed part and the darker part represents the relatively lower part. Due to the installation of the insertion outflow hole 5, the area where the insertion outflow hole 5 in FIG. 8B is brighter than that in the outflow hole in FIG. 8A is enlarged, that is, in the vicinity of the collision surface 3. Higher speeds increased significantly.

7 and 8, the insertion type outlet hole pipe 5 has a larger upward velocity component than the general type outflow hole, and in some cases, it is possible to solve the unbalanced heat / mass transfer distribution. It has been shown to affect.

9 (a) (b) and FIG. 10 (a) (b) are comparative tables of heat and mass transfer coefficient diagrams in terms of collision due to the array collision jet method and the insertion outlet hole installation and discharge method, respectively, as shown in the table. The very poor heat / mass transfer rate that appears in the downstream part of the transverse flow was able to obtain a uniform heat / mass transfer effect in the even area due to the insertion outlet hole pipe 5 installation.

11 is a graph showing local Sh values so that the distribution of Sh can be viewed in more detail. Here, Hm represents the height from the collision surface 3 to the inlet of the insertion outlet hole pipe 5. This is the result of the installation of the insertion outlet hole pipe 5 at H / d = 1.5. At Hm / d = 1.0, it is slightly larger than the outlet hole (Hm / d = 1.5). However, when Hm / d = 0.5, that is, the gap between the collision surface 3 and the outlet hole entrance is very narrow, it is very near the center of the insertion outlet hole pipe 5 (Fig. 12 (b), x / d = ± 3.0). Not only did they show high values, they also showed a significantly higher improvement in all areas. This can be seen to significantly reduce the re-suction flow by the insertion outlet hole pipe (5).

12 shows the overall average value for the case where the insertion outlet hole pipe 5 is present. In H / d = 1.5 and 2.0, the heat / substance is obtained when there is an insertion outlet hole pipe 5 (especially Hm / d = 0.5). Enhancement of delivery could be obtained. However, it can be seen that in narrow intervals such as H / d = 1.0, the adverse effect is caused by the increase of re-suction flow. By installing the insertion outlet hole pipe (5) with Hm / d = 0.5 at H / d = 1.5 and 2.0, the heat / mass transfer effect was increased by 13.25% and 5.08%, respectively. In addition, the average value of H / d = 1.5 to Hm / d = 0.5 was larger than that of the maximum value of the outflow hole installation method of H / d = 1. Therefore, an array collision jet with an insert outlet pipe can be evaluated as a new array collision jet technology that suppresses resorption flow compared to an array collision jet with a simple outlet hole.

According to the present invention, the arrangement collision jet discharge method according to the installation of the insertion outlet hole pipe suppresses the rise of the discharge flow in the vicinity of the outlet hole, thins the boundary layer thickness, and in particular, reduces the re-suction flow to reduce the overall average heat / mass transfer coefficient. There is a synergistic effect.

Claims (3)

In a colliding jet jet comprising a jet ejection plate having a cooling target collision surface, and having a plurality of jet holes which are spaced at arbitrary intervals with respect to the collision surface to cause the cooling fluid to strike the collision surface, The array collision jet, After the impact surface is cooled, a separate outlet hole pipe is inserted between the respective injection jet holes arranged in the jet jet plate so that the fluid exits in the horizontal direction and exits in the vertical direction without affecting other jets. It is installed by inserting type, The outflow hole pipe has an arrangement collision of the insertion outflow hole installation method, characterized in that it has a protrusion extending to the inlet side of the outlet hole pipe close to the impact surface in order to reduce the re-suction flow from the impact surface to the outlet hole of the outlet hole pipe. Z. The method of claim 1, The injection jet hole array collision jet of the insertion outlet hole installation method characterized in that it has a protrusion extending the inlet and outlet side to change the turbulence intensity and momentum of the flow. The method of claim 1, And a protrusion formed on the inlet side of the insertion type outlet hole pipe is treated with a gradient angle for extending the inlet area.